The most simple and straight-forward approach is using parzer library. For example, given points

library(parzer) 

latitude = "40°14'55.5"

lat_out = parse_lat(latitude)

longitude = "19°58'22.7"

lon_out = parse_lon(longitude)

Note: the direction is not required.

For more information, check https://semba-blog.netlify.app/02/25/2020/geographical-coordinates-conversion-made-easy-with-parzer-package-in-r/